This invention relates to a fuel injection timing control method for internal combustion engines, which is adapted to set the fuel injection timing to desired values.
A fuel injection timing control method for internal combustion engines has already been proposed in Japanese Provisional Patent Publication (Kokai) No. 56-148636, wherein the fuel injection timing is controlled in such a manner that the crank angle at which the fuel injection through the fuel injection valve is terminated is always maintained at a predetermined value slightly advanced from the crank angle at which the intake valve is closed, regardless of change in the engine rotational speed, to ensure positive ignition of the air-fuel mixture in the combustion chamber of the engine.
However, it has been empirically known that the optimal fuel injection timing differs depending on the specifications of the engine, such as the location of the fuel injection valves with respect to the intake valves, the configuration and size of the intake valves and their locations with respect to the fuel injection valves, and whether or not the engine is provided with sub-combustion chambers. Therefore, the conventional fuel injection timing control method has the disadvantage that, if fuel injection end is always maintained at a predetermined value as is the case with the conventional method, the engine cannot fully exhibit performance in respect of engine output, emission characteristics, fuel comsumption, etc, because the fuel injection timing determined by the fuel injection end maintained at the predetermined crank angle is not always optimal to the engine.